Effects of lunar dust simulant on cardiac function and fibrosis in rats

Numerical analysis of micro lunar dust deposition in the human nasal airway

The toxicity of Lunar dust (LD) is well-known to harm astronauts' health. However, the characteristics of micro-LD deposition in the human nasal airway remains unknown, and studying it through experiments is challenging. Therefore, this study employs numerical investigations to address this issue. Our findings reveal that LD larger than 4 µm primarily (>50%) deposit in the nasal cavity at an inspiration flow rate of Q= 40 L/min, while LD smaller than 8 µm are more likely (>50%) to enter the lung lobe at Q= 15 L/min. The right upper lung lobe receives a higher deposit fraction of LD compared to other lobes, reaching a maximum of 31%. The ratio of deposition fraction in the right lung and left lung can reach to 3.0. Accurately predicting LD deposition in the upper airway and entire lung is possible using mathematical expressions, but the prediction becomes more challenging for the bronchial airway and lung lobes. These results indicate that micro-LD deposition characteristics in the human nasal airway are influenced by LD size and astronauts' activity level. The deposition fractions can be used to assess the health risk from lunar dust to astronauts and provide insights into developing protective measures against LD exposure.

Exploring the mechanism of lung injury induced by lunar dust simulant in rats based on metabolomic analysis

Inflammatory response and oxidative stress are considered to be important mechanisms of lung injury induced by lunar dust. However, the pulmonary toxicological mechanism remains unclear. In the present study, Wistar rats were exposed to CLDS-i 7 days/week, 4 h/day, for 4 weeks in the mouth and nose. Lung tissue samples were collected for histopathological analysis and ultra-performance liquid chromatography-mass spectrometry analysis. Enzyme activities and expression levels of key metabolic enzymes were detected by biochemical analysis and real-time PCR. The pathological features of lung tissue showed that CLDS-i caused congestion and inflammation in the lungs, and the lung structure was severely damaged. Metabolomics analysis showed that 141 metabolites were significantly changed in the lung tissue of the CLDS-i group compared with the control group. Combined with Kegg pathway analysis, it was found that the changes of amino acid metabolites were involved in these pathways, indicating that the simulated lunar dust exposure had the most obvious effect on amino acid metabolism in the lung tissue of rats. Real-time PCR analysis showed that the mRNA expression of six key enzymes related to amino acid metabolism was changed, and the enzyme activities of these key enzymes were also changed, which were consistent with the results of qPCR. These results suggest that changes in amino acid metabolism may be closely related to the pathogenesis of lung injury induced by lunar dust, and amino acid metabolism may be a potential biomarker of lung diseases related to lunar dust exposure.

A Dusty Road for Astronauts

The lunar dust problem was first formulated in 1969 with NASA's first successful mission to land a human being on the surface of the Moon. Subsequent Apollo missions failed to keep the dust at bay, so exposure to the dust was unavoidable. In 1972, Harrison Schmitt suffered a brief sneezing attack, red eyes, an itchy throat, and congested sinuses in response to lunar dust. Some additional Apollo astronauts also reported allergy-like symptoms after tracking dust into the lunar module. Immediately following the Apollo missions, research into the toxic effects of lunar dust on the respiratory system gained a lot of interest. Moreover, researchers believed other organ systems might be at risk, including the skin and cornea. Secondary effects could translocate to the cardiovascular system, the immune system, and the brain. With current intentions to return humans to the moon and establish a semi-permanent presence on or near the moon's surface, integrated, end-to-end dust mitigation strategies are needed to enable sustainable lunar presence and architecture. The characteristics and formation of Martian dust are different from lunar dust, but advances in the research of lunar dust toxicity, mitigation, and protection strategies can prove strategic for future operations on Mars.